The invention relates to a device and a method for aligning optical beams. In particular, this invention relates to a general field of aligning optical beams for characterizing, testing, evaluating and applying linear and nonlinear optical materials and devices, electronic materials and devices, and mechanical materials and devices. Beam alignment is achieved using a device having either an elliptically curved or a parabolically curved mirror arranged in a reflected beam path between a rotatable mirror and the desired target. Combinations of both elliptical and parabolic mirrors may be used to solve a variety of beam steering and/or beam alignment problems.
Optical beams are typically steered by reflecting light from one or more moveable mirrors. Mirrors are moved or rotated with respect to the longitudinal axis of the optical beam path to produce a reflected or steered beam. The reflected beam is placed on a target material in accordance with the angle of rotation of the rotatable mirror. The rotatable mirror, often called a steering mirror, is typically the sole means for steering the reflected beam upon the target material. However, the steering mirror can be combined with a second mirror to direct the reflected beam onto the target material, wherein the second mirror is disposed within the reflected beam path and between the steering mirror and the target material. The second mirror, like the steering mirror, can be curved and can rotate independently or simultaneously with the steering mirror to optimally direct the reflected beam.
Merely reflecting optical beams by using a combination of rotatable mirrors and secondary mirrors does not provide adequate results in specific applications. Often it is desirable to place the reflected beam at a fixed position and vary, with a high degree of precision, the angle of incidence upon the target material. For ultrashort pulse non-linear optics experiments, for example, one must conserve momentum (phase matching) in addition to precisely controlling the temporal and spatial overlap of two or more beams upon the target material. Momentum is conserved by placing the various beams at the same position upon the target but at varying angles of incidence. Accordingly, a real need exists for an improved steering device and method which is also suitable for non-linear applications which can place an ultrashort optical beam at a precise point on a target but at varying angles of incidence.
In addition to being able to vary the angle of incidence upon a fixed target location, it is also highly desirable to direct a reflected beam at varying locations, but at a fixed angle of incidence. The reflected beam could be steered to arrive at different positions upon the target material while maintaining the same angle of incidence at each location. Like the variable angle, fixed position application, conventional steering techniques show difficulty in placing beams at variable positions upon a target while maintaining at fixed angle of incidence. In order to place reflected ultrashort beams evenly across a target, a real need exists for an improved steering device and method suitable for material and device characterization applications which can place an ultrashort optical beam at various points on a target while maintaining a fixed angle of incidence.